Measuring Apparatus

ABSTRACT

A measuring apparatus, in particular for measuring current, is provided. In at least one embodiment, the measuring apparatus includes a sensor and an evaluation device which is coupled or can be coupled thereto, in which the coupling is effected contactlessly, in particular by way of a transponder interface. As such, on the one hand current can be measured in a reaction-free manner, wherein on the other hand the resulting measuring apparatus can be used in a particularly flexible and versatile manner on account of the maneuverability of the components with respect to one another and on account of the relatively large possible distance between the two parts of the transponder interface.

PRIORITY STATEMENT

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DE2006/001291 which has anInternational filing date of Jul. 26, 2006, which designated the UnitedStates of America, the entire contents of which are hereby incorporatedherein by reference.

FIELD

At least one embodiment of the invention generally relates to ameasuring device. For example, at least one embodiment relates to ameasuring device for electrically isolated measurement of DC and/or ACcurrents, especially a measuring apparatus for measuring DC currentswhere there is a high insulation resistance.

BACKGROUND

The electrically isolated measurement of AC currents is possiblerelatively easily in a variety of ways. In the prior art, “Rogowskicoils”, which are transformer-type devices employing measuringtransformers etc., are known for this purpose. On the other hand, theelectrically isolated measurement of DC currents is far more complex. Tothe best knowledge of the applicant, only two methods are essentiallyused today for this purpose: one method is based on introducing a seriesresistor (shunt) in the current path and measuring the current-dependentvoltage drop; the other method is based on measuring thecurrent-dependent magnetic field using a magnetic field sensor, forinstance a Hall sensor or what are known as AMR/GMR sensors.

The problem with measuring across a shunt resistor is the directelectrical connection of the measuring points to the potential of thecurrent-carrying conductor. This requires electronic evaluationcircuitry having both an electrically isolated power supply and anelectrically isolated signal path for transmitting the measurements.

Using magnetic field sensors to measure the current has the advantage ofnon-interaction, i.e. there is no need to introduce a series resistor inthe current path to measure the current. As such, this thereby avoidsthe disadvantages associated with making a break in the line, the powerloss occurring across the shunt resistor and the change in the lineimpedance.

In addition, using magnetic field sensors benefits from the inherentadvantages of electrical isolation that are enjoyed e.g. when usingtransformers.

The problem with the magnetic field measurement, however, is thesensitivity of such magnetic field sensors to external fields andinterference fields. Suitable screening measures or field concentratorsmust be used to counteract this effect. In particular, it has provednecessary to position the magnetic field sensors as close as possible tothe current-carrying conductor, because the intensity of the magneticfield of a current-carrying conductor is known to decrease sharply withdistance (H˜1/(2πr)).

SUMMARY

At least one embodiment of the invention defines a measuring apparatusthat not only can be operated substantially with no interaction but alsois essentially immune to external fields and interference fields.

In at least one embodiment, a measuring apparatus, in particular ameasuring apparatus for measuring current, includes a sensor and anevaluation device which is coupled or can be coupled thereto, that thecoupling between sensor and evaluation device is effected withoutcontact.

An advantage of at least one embodiment of the invention lies in thefact that this coupling creates the opportunity of transferring powerand/or data, for instance measurements in the form of electronicsignals, without contact.

In at least one embodiment, for coupling purposes, the sensor has afirst transponder interface and the evaluation device has a secondtransponder interface. Coupling is then based on the transponderprinciple: the coupling is a transponder coupling, in particular basedon inductive or electromagnetic (radio) coupling.

If the first transponder interface assigned to the sensor is a passivetransponder interface, this first transponder interface and/or thesensor together does not have its own power supply, therebysubstantially avoiding interactions with the electrical values to bemeasured. The first transponder interface receives the power requiredfor the measurement via the second transponder interface of theevaluation device.

The sensor preferably includes a differential amplifier, which, in anadvantageous embodiment, is coupled or can be coupled to a line via ashunt resistor. In such a configuration, the measuring apparatusaccording to at least one embodiment of the invention can also be usedfor a measurement across a shunt resistor, which otherwise tends not tobe considered in connection with zero or low interaction measurementbecause of unavoidable interactions with the electrical values to bemeasured.

A magnetic field sensor, which is coupled or can be coupled to theconductor, is an alternative to the shunt resistor in at least oneembodiment. Using such a magnetic field sensor, in particular in anembodiment as a GMR sensor, creates the opportunity of measuring acurrent flowing through the conductor without any interactions, or atmost negligible interactions, with the conductor and the measuredelectrical values.

A particularly preferred embodiment is obtained if the sensor andevaluation device are each implemented as a separate physical unit. Thenthe sensor having the magnetic field sensor can be assigned to theconductor and the evaluation device can be assigned to the sensor bysuitable positioning.

At least some of the individual embodiments, in general, have theadvantage that the relatively large distance of the coupling based onthe transponder principle also allows both the sensor and the evaluationdevice to be implemented in an encapsulated and shock-proof form. Inaddition, the transponder coupling also allows a certain range ofmechanical movements between the sensor and the line. In certainembodiments, rotational movements or physical changes in location canalso be implemented.

For a sensor having a shunt resistor, the sensor together with thisshunt resistor can form a physical unit, for which no cable connectionswhatsoever are required between the evaluation unit and the live regionof the conductor measured in the measurement.

In addition, the sensor together with its transponder interface form asafe measuring point, from which readings can be taken using mobiledevices. An electronic circuit assigned to the sensor can also comprisea piece of identification information that is non-volatile inparticular, as is known from other transponder applications. By this, itis possible for a higher-level system to identify uniquely an individualmeasuring point, for instance the respective evaluation device, from agroup of measuring points. This is particularly useful when replacingcomponents or if the components or measuring points are moveable.

When measuring the current using a magnetic field sensor, in particulara GMR sensor, it is also advantageous for it to be possible to arrangethe current sensor in an optimally close position to the conductorcarrying or intended to carry the current, to a line, a conductor trackor a power rail or the like. Furthermore, the insulation between sensorand conductor only needs to be a purely functional isolation having avery low dielectric strength.

In addition, single-pole contact with the conductor is possible, becausethe safety function is performed by the transponder interface. Finally,the magnetic field sensor operates with completely no interaction unlikethe alternative embodiment having the shunt resistor.

The unavoidable additional resistance of the line with the shuntresistor and the resultant power loss do not occur with the magneticfield sensor. In addition, such a magnetic field sensor can easily bearranged in the vicinity of the respective conductor, and where theconductor is a power rail can even be retrofitted without the rail beingremoved.

Finally, magnetic field sensors in their embodiment as a GMR sensor,which is based on an operating principle that depends on the fielddirection (gradient field sensors), have advantages for the applicationas current sensors because they are extremely stable compared with largemagnetic fields and also the operating principle of the dependence onthe magnetic field direction can be exploited by arranging a pluralityof individual sensors specifically into a bridge circuit in order toachieve high immunity to external interference fields.

The patent claims submitted with the application are proposedformulations that do not prejudice achieving patent protection. Theapplicant reserves the right to claim yet further combinations offeatures hitherto only disclosed in the description and/or drawings.

The example embodiment or each example embodiment shall not be seen asrestricting the invention. In fact numerous variations and modificationsare possible within the scope of the present disclosure, in particularsuch variants, elements and combinations that, for example, by combiningor modifying individual features or elements or method steps describedin connection with the general or specific description part andcontained in the claims and/or the drawings can be gathered by theperson skilled in the art with regard to achieving the objective andthat lead to a new subject matter or new method steps or sequences ofmethod steps by combinable features, including where they concernmanufacturing methods for instance.

Back-references used in subclaims point to the further development ofthe subject matter of the main claim by the features of the respectivesubclaim; they shall not be seen as relinquishing achieving independentprotection of the subject matter for the feature combinations of thereferred-back subclaims. In addition, with regard to interpreting theclaims, where a feature is specified more precisely in a subsequentclaim, it must be assumed that such a restriction does not exist in eachof the preceding claims.

Since the subject matters of the subclaims in relation to the prior arton the priority date may form separate and independent inventions, theapplicant reserves the right to make them the subject matter ofindependent claims or declarations of division. They may also containindependent inventions, which have an embodiment that is independent ofthe subject matters of the preceding subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

An example embodiment of the invention is described in greater detailbelow with reference to the drawings. Corresponding objects or elementsare denoted by the same references in all the figures. In the drawings:

FIG. 1 shows a measuring apparatus for current measurement known in theprior art,

FIG. 2 shows a device for contactless current measurement using amagnetic field sensor,

FIG. 3 shows a first embodiment of a measuring apparatus according tothe invention having a contactless coupling between a part of themeasuring apparatus acting as a sensor and a part of the same measuringapparatus acting as an evaluation device,

FIG. 4 shows an alternative embodiment of the embodiment shown in FIG. 3using a GMR or magnetic field sensor, and

FIG. 5 shows a schematically simplified diagram of the embodiment ofFIG. 4, where the sensor and the evaluation device are each implementedas a separate physical unit.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

FIG. 1 shows a measuring apparatus 10 known in the prior art formeasuring the current I flowing through a conductor 12 (currentmeasurement). The known measuring apparatus is based on a shunt resistor14 present in the conductor 12, across which resistor the voltage dropis measured and transferred via a differential amplifier 16 to ananalog-to-digital converter 18, from where the data encoding themeasured current is transferred in sequential form e.g. via an opticalfiber 20 to a digital-to-analog converter 22 and from there to avoltage-current converter 24. The apparatus 10 also comprises anoscillator 26, a voltage regulator 28, a sine wave generator 30 and arectifier/filter 32 which is fed from the generator and provided for thepower supply. The measuring apparatus 10 as a whole is divided into afirst part 34 and a second part 36, where the first part 34 performs thesensor function and is physically assigned to the conductor 12, andwhere the second part 36 performs the evaluation-device function and canbe arranged remotely from the first part 34 acting as the sensor.

FIG. 2 shows in a simplified diagram the use of a magnetic field sensor38 for current measurement, whose output is connected to a differentialamplifier 16, a servo circuit or the like. The magnetic field sensor 38,which is implemented in particular in a form as a measuring bridgecontaining a plurality of individual magnetic field sensors (gradientfield sensor), measures the magnetic field H around the conductor 12.According to the relationships known per se, the current I can bederived from the strength of the magnetic field, so that the currentmeasurement actually intended is possible.

FIG. 3 and FIG. 4 show the implementation according to an embodiment ofthe invention of the measuring apparatus, in which a first part, actingas a sensor 40, of the measuring apparatus denoted as a whole by 10, iscoupled without contact to a second part, acting as an evaluation device42, of the measuring apparatus 10. This contactless coupling is achievedby the fact that the part acting as the sensor 40 has a firsttransponder interface 44, and the part acting as the evaluation device42 has a second transponder interface 46. The first transponderinterface 44 assigned to the sensor 40 is preferably implemented so thatthe sensor 40 receives its power via the evaluation device 42 and itstransponder components 46.

The embodiment shown in FIG. 3 is based on a measurement of a current Ithrough a conductor 12 via a shunt resistor 14. The sensor 40 comprisesa differential amplifier 16 for evaluating the voltage drop across theshunt resistor 14 and, if applicable, further elements (not shown) fromthe diagram in FIG. 1, which is more detailed in this respect.

FIG. 4 shows the embodiment in which the current is measured bymeasuring the magnetic field H generated by the current I. For thispurpose, the sensor 40 (cf. FIG. 2) has a magnetic field sensor 38, ifnecessary in an embodiment as a measuring bridge containing a pluralityof individual magnetic field sensors, and a differential amplifier 16,which, if applicable, in a similar way to the embodiments above for FIG.3, may comprise further components from the diagram in FIG. 1, which ismore detailed in this respect.

FIG. 5 shows an embodiment in which sensor 40 and evaluation device 42are implemented as a separate physical unit and in which the sensor 40comprises a GMR sensor as the magnetic field sensor 38 and is assignedto a conductor 12 in the form of a power rail, a conductor track or thelike. An insulating layer 50 is provided between the magnetic fieldsensor 38 and the conductor 12, which acts as a functional isolationbetween conductor 12 and magnetic field sensor 38. Sensor 40 andevaluation device 42 are each constructed on a separate printed circuitboard 52, 54, where in the diagram of FIG. 5, the representation of theprinted circuit board 52, 54 also includes the representation of therespective transponder antenna.

The transponder interface, identified in FIG. 5 by the verticaldouble-ended arrow, is obtained between the printed circuit boards 52,54 and the transponder antenna formed by them, at least partially inthis respect. The sensor 40 and a sensor and transponder circuit 56 ismounted e.g. in the form of an ASIC on the printed circuit board 52 ofthe sensor 40. A GMR layer acting as a magnetic field sensor 38 can beapplied directly to this circuit 56. The transponder circuit on theevaluation-device side, i.e. the second transponder interface 46, ismounted, in particular in the form of an ASIC 58, on the printed circuitboard 54 of the evaluation device 42.

At least one embodiment of the present invention can be summarized asfollows: a measuring apparatus 10, in particular for currentmeasurement, is defined, having a sensor 40 and an evaluation device 42which is coupled or can be coupled thereto, in which the coupling iseffected without contact, in particular via a transponder interface 44,46, so that not only is it possible to measure the current withoutinteraction but the resulting measuring apparatus 10 can be used in aparticularly flexible and versatile manner by virtue of thecomparatively large distance possible between the two parts of thetransponder interface 44, 46.

Example embodiments being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the present invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

1. A measuring apparatus, comprising: a sensor including a differentialamplifier; and an evaluation device, at least one of coupled andcoupleable to the sensor, wherein for non-contact coupling of the sensorand the evaluation device, the sensor includes a first passivetransponder interface and the evaluation device includes a secondtransponder interface, and wherein the differential amplifier being atleast one of coupled and coupleable to a conductor via a magnetic fieldsensor.
 2. The measuring apparatus as claimed in claim 1, wherein themagnetic field sensor is implemented as a GMR sensor.
 3. The measuringapparatus as claimed in claim 1, wherein sensor and evaluation deviceare each implemented as separate physical units, and wherein the sensor,including the magnetic field sensor, is assigned to the conductor andwherein the sensor is assigned to the evaluation device by suitablepositioning. 4-8. (canceled)
 9. The measuring apparatus as claimed inclaim 2, wherein sensor and evaluation device are each implemented asseparate physical units, and wherein the sensor, including the magneticfield sensor, is assigned to the conductor and wherein the sensor isassigned to the evaluation device by suitable positioning.
 10. Themeasuring apparatus of claim 1, wherein the measuring apparatus is formeasuring current where there is a high insulation resistance.
 11. Themeasuring apparatus of claim 2, wherein the measuring apparatus is formeasuring current where there is a high insulation resistance.
 12. Themeasuring apparatus of claim 3, wherein the measuring apparatus is formeasuring current where there is a high insulation resistance.
 13. Themeasuring apparatus of claim 9, wherein the measuring apparatus is formeasuring current where there is a high insulation resistance.
 14. Themeasuring apparatus of claim 1, wherein the coupling creates a conduitfor transfer of at least one of power and data.
 15. A sensor for ameasuring apparatus, comprising: a differential amplifier at least oneof coupled and coupleable to a conductor via a magnetic field sensor;and a passive transponder interface to couple the sensor to atransponder interface of an evaluation device of the measuringapparatus.
 16. The sensor as claimed in claim 15, wherein the magneticfield sensor is implemented as a GMR sensor.
 17. The sensor as claimedin claim 15, wherein the sensor and the evaluation device are eachimplemented as separate physical units.
 18. An evaluation device for ameasuring apparatus, comprising: a transponder interface to couple, in anon-contact manner, the evaluation device to a passive transponderinterface of a sensor of the measuring apparatus, wherein a differentialamplifier of the sensor is at least one of coupled and coupleable to aconductor via a magnetic field sensor.
 19. The evaluation device asclaimed in claim 18, wherein the magnetic field sensor is implemented asa GMR sensor.
 20. The evaluation device as claimed in claim 18, whereinthe sensor and the evaluation device are each implemented as separatephysical units.